Current or future wireless networks, such as beyond 3G mobile radio system, may require considerably large coverage areas and high data rate. A relay network may be employed for current and future demands. Incorporating fixed or mobile relays in the network may e.g. be a modification in the wireless network architecture to meet desired high throughput and coverage requirements for actual or future application. In relay networks, a relay node, RN, is provided which forwards data or signalling from a source node, SN, to a destination node, DN, which is out of reach of the SN.
Random access protocols are widely used in a cellular network for initial access, bandwidth request, location update, etc. However, random access schemes may have problems regarding user collision which reduces the throughput. Moreover, the collision may also result in an uncontrollable access delay which makes it difficult to meet quality of service, QoS, requirement for an attempted user.
In a cooperative network, user collision may become problematic when a random access is relayed to a base station, BS, because the collision consumes not only resources of the random access channel in the system but also causes high overhead of the link establishment between the source user and the relay node during the initial random access. Furthermore, the access delay may become uncontrollable if the user needs to re-establish the communication with the relay node before retransmission. Therefore, it is desirable to reduce user collision in the relaying network and the number of unnecessary retransmission for the random access should also be minimized.